1. Field of the Invention
The present invention relates to compositions for the cosmetic or dermatological treatment of imperfections or complaints of the skin, including the scalp. It relates more particularly to a composition for combating ageing, comprising at least one active agent which is conveyed via at least two distinct types of lipid vesicles. The present invention also relates to the use of this composition for combating ageing of the skin, and to a method for combating the ageing of the skin by applying such a composition to the skin.
2. Discussion of the Background
Many examples are known of cosmetic or dermatological compositions intended for treating the skin, which have one or more active agents that are suitable for treating the skin and which are encapsulated in lipid spherules or vesicles (also known an liposomes).
Lipid spherules or vesicles are understood to refer to particles formed of a membrane consisting of one or more concentric lamellae, these lamellae containing one or more bimolecular layers of amphiphilic lipids encapsulating an aqueous phase. The aqueous phase may contain water-soluble active substances, and the bimolecular layers of amphiphilic lipids may contain lipophilic active substances.
These spherules generally have a mean diameter of between 10 nm and 5000 nm. Among the many documents published regarding this matter, there may be mentioned the French Certificate of Addition 2,408,387 which describes a composition based on aqueous dispersions of ionic or nonionic lipid spherules encapsulating at least one active substance. More precisely, this document describes compositions containing at least two dispersions of spherules containing different active agents, for the purpose of obtaining a mixed system, that is to say a system in which a first dispersion of spherules containing a first type of active substance is combined with a second dispersion of spherules containing another type of active substance, which enables the two types of substances to act simultaneously at the time of treatment and possibly to obtain a synergic effect which would not be produced if these two types of substances were made to act successively and separately.
It is known that during the ageing process various signs which are very characteristic of this ageing appear on the skin, reflected especially in a modification of the cutaneous structure and function. This ageing is physiological in nature but is also photo-induced, that is to say that it is due to the repeated exposure of the skin to light and, consequently, to the formation of oxygenated free radicals via the action of this light on the constituents of the skin.
The main clinical signs of cutaneous ageing are especially the following: appearance of deep wrinkles which increase with age. In particular, disruption of the "grain" of the skin in observed, that in to say that the microrelief is less uniform and is anisotropic in nature.
Moreover, the skin complexion is generally modified; it appears paler and yellower, which appears to be due essentially to disruption of the microcirculation (less haemoglobin in the dermal capillaries). Many colored blemishes appear at the skin surface, due to impaired melanogenesis. Diffuse irritations, and sometimes telangiectasia, occur in certain areas.
Another clinical sign of ageing is the dry and rough appearance of the skin, which is essentially due to a more considerable desquamation; by diffracting light rays, these squama also contribute towards the somewhat grey appearance of the complexion.
Finally, a loss of firmness and of tonicity of the skin are observed which, as for wrinkles, is at least partly explained by a dermal and epidermal atrophy and a flattening out of the dermoepidermal formation.
It is thus observed that the clinical signs of cutaneous ageing result essentially from a dysfunction of the main biological mechanisms involved in the skin.
It is well known that the skin consists of surface layers, the stratum corneum, and of deep layers, the live epidermis and the dermis. However, specific delivery of such an active agent into the surface layers and, simultaneously, of the same or another active agent into the deep layers, was not known from the prior art.
Thus, there remains a need for a method of combating the aging of the skin which simultaneously acts on the surface layers and the deep layers of the skin. There also remains a need for compositions useful in such methods.